Continuous data protection enables a user to be able to access or restore a previous state with finer time granularity than previously offered by some traditional backup solutions. For example, some traditional backup solutions perform backups at discrete points in time that are separated by hours or even days. The only previous states that a user is able to restore are the states corresponding to those points in time. With continuous data protection, data (e.g., a file or other data associated with a continuously protected device) is continuously protected over a window of time and a user is able to access almost any prior state within that window. For example, using some continuous data protection systems a user can access or restore saved states that are seconds or fraction of seconds apart.
To continuously protect data, previous version data typically is obtained and stored in allocated storage. In some cases, there is a significant amount of previous version data that needs to be stored. Typically, storage used to store previous version data is reclaimed as the data stored in particular locations is no longer required to be retained, e.g., because it relates to states that fall outside (i.e., prior to the earliest/beginning edge of) the rolling window described above. However, in some cases previous version data that falls outside the continuous data protection window may need to be retained, e.g., because a user has indicated the data is desired to be available to be used to restore a data set or one or more data objects comprising the set. The need to retain data outside the protection window may lead to inefficient reclamation and reuse of storage, e.g., if the previous version data required to be retained breaks up a section of storage that otherwise could be reclaimed as a group into smaller chunks each of which must be reclaimed and reallocated separately. Therefore, there is a need for a way to efficient reclaim and reuse storage used to store previous version data, including where some older previous version data is required to be retained.